Lawsplainer: "Fruit of The Poisonous Tree" And The Special Counsel Investigation

Then there's the concept that the "fruit of the poisonous tree" doctrine allows exclusion of specific evidence resulting from violation of a particular defendant's rights. It doesn't require the shutting down of entire investigations.

Put another way, the question is whether the defendant can draw a direct line between a violation of his or her rights and a piece of evidence. The courts have rejected a "but for" theory of the doctrine. That is, the question isn't "would the police have done the things they did but for the violation of my rights." "The Court has never held that evidence is 'fruit of the poisonous tree' simply because “it would not have come to light but for the illegal actions of the police.'" So, for instance, even if the police become interested in searching my house because of evidence they seized illegally from me, so long as the warrant application to search my house does not include any of the illegally seized evidence, it's not fruit of the poisonous tree.

There's a related concept called attenuation. "Evidence is admissible when the connection between unconstitutional police conduct and the evidence is remote or has been interrupted by some intervening circumstance." The most common example of this is a voluntary statement. Generally, if the police illegally seize evidence, and then come and ask me about it, and I make a voluntary statement, courts consider the connection between the illegal seizure and the statement attenuated by my voluntary act, so that my statement is not suppressed. So, in the case of the Special Counsel, Papadopoulos and Flynn pleaded guilty to lying to the FBI during voluntary statements to them. Even if the Special Counsel got to that interview by violating rights, and even if those were Papadopoulos's and Flynn's rights, the voluntary statements would generally be treated as breaking the chain and would be admissible.